Clay illuviation provides a long-term sink for C sequestration in subsoils

• Published in: Scientific reports Vol. 7; no. 1; p. 45635
• Main Authors: Torres-Sallan, Gemma, Schulte, Rogier P. O., Lanigan, Gary J., Byrne, Kenneth A., Reidy, Brian, Simó, Iolanda, Six, Johan, Creamer, Rachel E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.04.2017; Nature Publishing Group
• Subjects: 704/172/169; 704/47/4113; Carbon; Carbon cycle; Clay; Climate; Climate change; Climate change mitigation; Farming Systems Ecology; Grasslands; Humanities and Social Sciences; Intergovernmental Panel on Climate Change; Land management; Land use planning; Leerstoelgroep Farming Systems Ecology; LEI Performance and Impact Agrosectors; LEI Performance en Impact Agrosectoren; Mineralization; multidisciplinary; PE&RC; Performance and Impact Agrosectors; Performance en Impact Agrosectoren; Science; Silt; Subsoils; Topsoil
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep45635

Soil plays a key role in the global carbon (C) cycle. Most current assessments of SOC stocks and the guidelines given by Intergovernmental Panel on Climate Change (IPCC) focus on the top 30 cm of soil. Our research shows that, when considering only total quantities, most of the SOC stocks are found in this top layer. However, not all forms of SOC are equally valuable as long-term stable stores of carbon: the majority of SOC is available for mineralisation and can potentially be re-emitted to the atmosphere. SOC associated with micro-aggregates and silt plus clay fractions is more stable and therefore represents a long-term carbon store. Our research shows that most of this stable carbon is located at depths below 30 cm (42% of subsoil SOC is located in microaggregates and silt and clay, compared to 16% in the topsoil), specifically in soils that are subject to clay illuviation. This has implications for land management decisions in temperate grassland regions, defining the trade-offs between primary productivity and C emissions in clay-illuviated soils, as a result of drainage. Therefore, climate smart land management should consider the balance between SOC stabilisation in topsoils for productivity versus sequestration in subsoils for climate mitigation.